1. Technical Field
The present invention relates to a robot control system for controlling an industrial robot (which will be hereinafter referred to simply as “robot”), and specifically, relates to a robot control system having a stop function.
2. Description of Related Art
In general, a robot control system monitors a shaft speed of a robot or a speed of a robot arm. If the speed exceeds a predetermined threshold value, the robot is stopped to thereby maintain the safety of an operator.
Japanese Unexamined Patent Publication (Kokai) No. 2009-50958 discloses that a servo motor is stopped based on the position of the servo motor detected by a position sensor provided on the servo motor.
In this connection, the shaft speed of the robot or the speed of a robot arm is calculated based on the result of the actual movement of the robot. Therefore, even if the robot is stopped, as mentioned above, a slight movement of the robot takes place before the robot actually stops. In Japanese Unexamined Patent Publication (Kokai) No. 2009-50958, as the servo motor is interrupted based on the position of the servo motor, there is a problem that a slight movement of the servo motor occurs before the shaft of the servo motor is stopped. Under these circumstances, the safety of an operator may not always be maintained.
The present invention has been made in view of the foregoing, and it is an object of the invention to provide a robot control system which is capable of stopping the robot before the servo motor begins operating.